Signal reproducer



Oct. 4, 1932. H E, METCALF 1,881,324

SIGNAL REPRODUCER Filed OOC. 25, 1927 INVENTQR 7V ra/* f. Ale/dar BY gn HIS ATTORNEY Patented Oct. 4, .1932' ,UNITED STATI-:s yPrl'lizNr, lori-*1er l HERBERT E. HETCALF, F SAN LEANDWBO, CALIFORNIA, ASSIGNOR TQ THE MAGNAVQX COMPANY, 0F OAKLANI), CALIFORNIA, A CORPORATION 0F .ARIZONA SIGNAL BEPRODUCEB 'Application mea october 2s, 1927. serial No. 228,872.

This invention relates to reproduction of electric signals, and-v' especially lto a device whereby telephonie currents are converted into sound of large volume.

One form of reproducer or loudspeaker utilizes the dynamic principle for moving an air actuator, such as a diaphragm or cone. In this form of speaker, there is provided a. magnet, (eitherl permanent or electromagnetic) which provides an intense and constant -magnetic lield across a narrow air gap. A movable coil is-disposed-in this field, and is fed with the currents that are to be translated into sound waves. The reaction between the varying magnetic ieldproduced by this coil and the magnetic field of the constant magnet causes movement of the coil, which in f turn imparts movement to the air actuating device mechanically connected to` the coil. 2o Since the movement of the coilfollows in accordance with the variations of the currents fed thereto, it is evident that faithful reproduction is'obtained. v

It is of course to be understood that the device is reversible infunction; that is, sound waves can be convertedvinto electric impulses by actuating the coil in accordance with these waves. y f It is one of the objects of my invention so to improve in generalthis form of reproducer. It is another object of my invention to provide an improved mechanical arrangement of the elements making up t-he speaker; and especially to provide a convenient form of mov- .'25 able support for the movable coil, and to arrange the connections thereto in such a way that there shall be no undesirable rattling or other extraneous sounds.

My invention poesses many other advantages, and has other objects which may be made more easily apparent from a consider- .ation of one' embodiment of my invention. For this purpose I have shown a form in the drawings accompanying and forming part'V of the present specification. I shall now procecd Lto describe this form in detail, which fxillustrates the general principles of my invvention: but it is to be understood that this detailed description 'is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a side view, part-l in section, of a dynamic loud speaker em odying my invention;

Fig. :2 is an enlarged detail, partly in section, `showing' the manner in which the coil supporting parts are arranged;

Fig. 3 is a view taken from the left of Fig. 2; and

Fig. 4 is a plan view vof the flexible mounting member utilized for suspending the movable coil.

AIn this instance I show a conetype speaker, although other forms of speakers could be e5 used in connection with my invention. In order to provide the strong constant magnetic field, there is an electromagnet arrangement.. including a central core 11, and a coil 12 disposed around this core. An annular 70 air gap is formed around core 11 so as to provide radial lines of force between the reduced portion 13 of corelll and a surrounding circular pole piece 14 of magnetic material. This pole piece is supported on the -cylindrical housing 15. as by aid of the'brackets 16. This housing also serves to complete the magnetic circuit, and to support the coil 12, thus forming a typical iron-clad magnet. A flange 1T disposed around core 11 and tting 30 snugly into housing 15v serves effectively to maintain the annular` air Vgap between core end 13 andpole piece 14 uniform.

The coil that carries the telephonie currents is tubular in form so as to permit it to 35 encompass the extension 13 and thus to place its conductors transversely to the radial lines of force in the air gap. For this purpose, a coil 18 (Fig. 2) of line copper wlre. is wound in a groove on the outer surface of a hollow o0 cylindrical support- 19. kThis support or spool is made from insulating material, such as bakelite, and is thin enough to pass easily between the pole piece 14 and the core extension 13. It is now well known that a varia- Vtion in current fiow in coil 18 will cause a.

, 19 in an axial direction.

ment cone. The coil structure, including support 19, can be mechanically connected to the air actuator; and one of the features of my invention resides in the manner in which the coil assembly is attached to the air actuator.

In this instanceI show a cone 2O as of stiff paper or parchment, serving as the air` actuator. Its edge can be left free if desired, but I vindicate it as fastened as by pasting, to a leather belt 21, which in turn is confined between the support 22 and the ring 23. The

smaller end'of the cone is glued or otherwise fastened to the inside of a metal conical cap 24. This cap can be provided with a series of apertures 25 to permit any excess fastening fluid to escape from between it and the cone 20. n

' The cap 24 has a tubular extension 26 (Fig. 2), between which and the conical portion there is an annular straight shoulder 27. The support 19 telescopes with theextension 26, as by being disposed thereover. A series of prongs 28 struck up from extension 26 can be engaged in apertures 29 in support 19,

. to ensure against relative axial movement of these parts. However, the same result can be obtained by providing a tight lfit between the parts 19 and 26. i y

In order to guide the coil 18 and its support I prefer t0 hang it flexibly, as by the aid o-f a flexible washer 30 shown in detail in Fig. 4. This washer has an inner ring portion 31 that fits over shoulder 27 and is clampedbetween it and the end of tubular support 19. The washer is also provided with an outer annular portion 32 where it can be clamped between the opposing faces of a clamping ring 33 (Fig. 1) and a flange 34 (Figs. 1 and 3) formed on a. supporting ring 35'. This clamping can be effected by the aid of a series of screws 36 tapping into flange 34.` The ring 35 can in turn e conveniently fastened on the outer surface of pole piece 14, as by the aid'of screws 37 engaging the ears 38 of ring 35. These ears are offset from the flange 34 so as to space the pla-ne of washer 30 correctly with respectto the desired axial position ofrcoil 18.

The twoannular portions 31 and y32 of washer 30 are connected by a series of relatively long, flexible connections 39 (Figs. 3

and 4). Since the ywasher is made from thin flexible material, such as bakelite or varnished cambric, it is evident that although the rim 32 is confined against movement, the

inner ring 31 can be flexed axially due to the give of the connections 39. This give is sufli-` cient to permit the coil 18 to move axially in accordance with the telephonic'currents. It should also be noted that the connections 39 are nonradial, whereby their effective length is large and-whereby great flexibility isassured. It is also evident that the movement of-coil 18 is guided due to this flexible susvpension so that it will `remain properly cenpointed out that the connections or strips 39 are so disposed with respect to the coil and thefixed points that they are, when fixed to permit axial movement of the coil 18, subjected to twisting strain, which permits the coil to move axially without at the same time perlmitting any radial displacementof the co1 The two leads for coil 18 can be veryv conveniently brought \out for external connections, and in such a way as to prevent any rattling in the reproduction. Thus the leads 40, 41 can each be accommodated in a groove such as 42, cut or otherwise formed on the exterior of support 19. These grooves connect at their left hand end with the annular depression in which the turns are supported, and at their right hand end, they serve to conduct the bare leads to the washer 30. The leads can be pasted or shellacked onto .the washer, preferably along the arms 39, as shown most clearly in Fig. 3. If necessary, a fabric covering 43 .can be fastened over this portion of the leads. "A pair of eyelets or bushings 44 is provided, one adjacent .the outer end of each of a air of connecting members 39, for permitting the passa e of the leads and 41 to the 4outside o the washer 30, as clearly indicated in Fig. 1. These leads can then be fastened to any appropriate external terminals.

I claim:

1. In a signal transmitting device, means forming an annular magnetic air'gap, a coil structure axially movable in said 4gap and arranged to carry the signaling currents, means flexibly supporting said structure, said means having a portionI that is confined against movement, another concentric portion that is fastened to the coil structure, the

.two` concentric portions being substantially -1 coplanar,and flexible connections between said'two portions; and leads for the coil fas-v tened to said flexible connections.

2. In a movable coil structure for dynamic reproducers, a tubular spool, a coil wound on said spool, a supporting member telescoping with one end ofthe tubular spool and supporting it, and a flexible guiding suspension for` the coil fastened between the end of the spool and an annular shoulder on port. o

3. In a dynamic reproducer, amovable coil structure, and a flexible supportfor the structure, including a washer of flexible material, said washer having an inner annular portion fastened to the coil structure, an outer an' nular portion spaced from the inner portion, said outer portion being adapted to be supported on a stationary "support, and flexible arms connecting .the inner and outer porthe sup.-

tions, said arms departing from radial direction in order to increase their effective length.

a non-radial direction to a support, said Hexible members being disposed ina plane sub- .'stantially 'at right angles to the direction of movement of the coil and having a length greater than the radial distance beteen'said coil and said support.

5. In a loud speaker of the electromagnetic type, the combination of 7a coil ada ted to move in a magnetic Held, a. support or said coil-having Hexible portions extending from said coil to fixed points, said Hexible ortions being of a length greater than the ra ial distance between said coil and said fixed points,

and current carrying leads for the coil) :fas-

tened to and extending along certain of the Hexible portions-between the coil and said fixed points.

6. In a loud speaker of the electro-magnetic type, the combination of a coil adapted to move in a ma etic field, and a support for saidl coil havino' spirally disposed Hexible portions extendingfrom said coil to a fixed point, said Hexible portions extending substantially tangentially with respect to the axis of said coil wherebytheir Hexibility is greatly increased.

7. A sound reproducer having a conical diaphragm, a magnetic driving means for said diaphragm, and means for supporting said diaphragm, said supporting means including a Hexible support having aplurality of members, said membersbeing non-radial with respect to the axis of said diaphragm,

and inclined in a common direction with re-v spect to their corresponding radii.

" phragm, said supporting means including a Hat Hexible support having a plurality7 of members, said members bei ng non-radialwith respect to the axis of said diaphragm and inclined in a common direction with respect to their corresponding radii.`

10. A sound reproducer having a conical diaphragm, a driving device for said diaphragm, and means for supporting said diaphragm, said supporting means including a Hexible support having a plurality of members, said members being non-radial with respect to the axis of said diaphragm, and inclined in acommon direction with respect to their corresponding radii and spacally separated for at least a part of their lengths.

11. A sound reproducer having a conical diaphragm, fa driving device for said diaphragm, and means for supporting said diaphragm, said supporting means including a Hat Hexible support having a plurality of members, said members being non-radial with respect to the axis of said diaphragm and inclined in a common direction with respect tol their corresponding radii and spacially separated orat least a part of their lengt-hs.

12. A sound reproducing device having a conical diaphragm, a driving device for said diaphragm, and means adjacent the small end of said diaphragm for supporting said diaphragm, said supporting means including means for permitting said diaphragm to rotate slightly about its axis as the diaphragm reciprocates in the direction. of its axis.

13. In an apparatus for sound reproduction. a substantially rigid diaphragm having the form of a cone and adapted to vibrate as a whole, means for actuating said diaphragm comprising a pair of concentric pole pieces separated by an annular air gap, an actuating coil secured to the small end of said diaphragm and located in said air gap, and means for preventing lateral movement of said coil in said air gap including a.l support, said support having a plurality of Hat Hexible members all extending non-radially in the same cyclic sense with respect to the axis of the diaphragm.

14. In a loud speaker of the electro-magnetic type, the combination of a coil adapted to move in a magnetic Held, and supporting means for said coil'comprising Hexible members extending outwardly with respect to the longitudinal .axis of said coil, said Hexible members extending in a non-radial direction between said longitudinal axis and a support, said Hexible members being disposed substantially at right angles to the direction 'of movement of the coil and having a length greater than the radial distance between said longitudinal axis and said support.

l5.. In a signal transmitting device, means .forming a magnetic air gap, a current-carrying coil adapted to move in said air gap, and a yielding support for said coil comprising Hat strips' of non-elastic Hexible material extending outwardly with respect to the longitudinal axis of said coil, said Hat strips extending to Hxed points, said strips being positioned with respect to the coil and Hxed points so that a twisting strain will be imposed upon said strips as the coil moves axially in said gap.

16. In a loud speaker of the 'electromag- Y netic type, an element adapted for reciprocal movement, and yielding supporting means for said element comprising a flat strip of ilexible material extending from a point at which it is secured for movement with said element to a fixed support, said strip being disposed in a plane transverse to the direction of 'movement of the element and` being positioned with respect to the element and said supportso that a twisting strain will be im-` posed upon the strip as the element reciprocates.

17. In a loudv speaker of the electromagf netic type, an element adapted for reciprocal movement, and yielding supporting means for said element comprising a spirally disposed fiat strip of flexible material extending from a point at which it is secured for movement'with said element to a support, said 20 flexible strip being'disposed in a plane subv stantially at right angles to the direction `of f -movementofthe element and, having a "length greater than thesti'aight line distance between the support and the point at which it is secured for movement with the'element.

.18. In a loud speaker ofthe electromagnetic type, the combination-of a substantially ,cylindrical shaped current-carrying coil adapted to reciprocate in a magnetic field and along an'axis common to the axis of the coil, 4and yielding supporting means for said coil holding the, coil against radial displacement With/respect", to said axis as the coil reciprocates and comprising flat strips of flexible ,material extending from pointsf'at .which they,

I, are secured for movement withws'aid coil to fixed supporting means positioned about said v 'axis, said strips being` positioned with respect to the 'coil and lixed supporting means so that-- a twisting strain will be imposed upon said strips as the coil` reciprocates. Y y

19. LIn al'oud speaker of the electro-magnetic type, the combination of a coil adapted to move in amagnetic eld, and a support {for said coil 4having spirally disposed flexible iportions extending from said coil to a fixed location, said flexible portions being of af' -length greater than the radial distance between said coil and said fixed location.

20. In a signal transmitting device, means forming a/magnetic air gap, a current-carryying coil adapted to move in said air gap, and a yielding support for said coil comprising fiat strips of flexible material extending outwardly from said coil to fixed points, said strips vbeing positioned with respect to the "coil and fixed points so that a twisting strain 'will be imposed np'on said strips as the coil moves axially in said gap.

2l. In an instrument of the class described,

the combination of a conical diaphragm,

means to actuate the diaphragm comprising gap for movement in the direction of movement of the axis of the diaphragm, a iiexlble aligning device permitting movement of the coil in the desired direction and restraining yany movement in 'a direction transverse thereto, and current carrying leads for the coil ends connected to the latter at points secured to the aligning device.

22. A sound reproducer comprisin a substantially conical diaphragm, means orming a magnetic air gap, a current carrying member secured to the diaphragm adjacent its apex and disposed in the gap for movement in the direction of the axis ofthe diaphragm, means for maintaining the current carrymg member in spaced position Within the gap, comprising a plurality of flexible arms extending out from said current carrying member to fixed supporting means,.and leads for coil secured to` said diaphragm and adapted` to move in said air gap, an outwardly extending flexible centering support for said coil, and flexible leads from an external circuit connected tothe ends of said actuating coil at points along said flexible centering suport.v f p 24. In a loud speaker of the electromagnetic type, an'element adapted for reciprocal movement and yielding supporting means for said element comprising flexible members extending non-radially with respect to the axis of said element from a point at which they are secured for movement with4 said element to a fixed support, said flexible members being disposed in a plane substantially at right Yangles to the direction of movement of the element and having a length greater than the straight line distance between the support *and the points at Awhich they are secured for 4movement Ywith the element.

.25., A sound reproducer comprising a substantially conical diaphragm, means forming a magnetic air gap, anactuating coil secure to the diaphragm adjacent its apex and dismy hand.

HERBERT E. METCALF.

a current carrying coil of relatively fine wire' secured tothe diaphragm adjacent the apex of the latter and disposed in a magnetic air 

